1. Field of the Invention
The present invention relates generally to a mold insert for molding multi-fiber ferrules, and more specifically, to a precision insert for molding angled and bumpered multi-fiber ferrules and associated methods of manufacture.
2. Technical Background
Fiber optic cables require optical connectors or ferrules to link discrete segments of optical fibers. As used herein, the term “ferrule” refers to a component of a connector assembly that receives a terminal end of one or more optical fibers or an optical fiber ribbon and aligns with an opposing ferrule to optically couple corresponding optical fibers to transmit an optical signal or signals. In order to minimize signal losses across a ferrule-to-ferrule optical connection, it is important that the opposing optical fibers be precisely aligned. The precision of opposing optical fibers is more sensitive with multi-fiber ferrules due to the presence of multiple optical fibers and the tolerance buildup associated the location of each fiber relative to the other fibers and relative to a common axis.
Referring to FIGS. 1a-b, a prior art multi-fiber ferrule 10 typically includes a plurality of optical fibers arranged in one or more rows along the end face 12 of the ferrule. The “end face” of the ferrule refers to the portion of the ferrule that includes the optical fiber bores 11 and is disposed between a pair of openings 13 for receiving guide or alignment pins. The portion of the end face including and adjacent the optical fiber bores 11 is referred to herein as the “region of interest” 14 (see FIG. 1b) and in the prior art ferrules shown, is altered after molding by contact during subsequent machining and polishing processes. Ferrules may be produced having an end face 12 perpendicular to the longitudinal axis of the ferrule body. As shown, ferrules may also be produced having an end face 12 with an angle other than perpendicular to the longitudinal axis of the ferrule body, such as an end face having an angle of about 8 degrees based on industry standards. Ferrules may also be produced with an end face 12 having both a flat (perpendicular) portion and an angled portion. The angle is typically introduced into the end face 12 of the ferrule body by machining (e.g., grinding) the end face a flat ferrule subsequent to the ferrule molding process. By machining the angle in as opposed to molding the angle, the end face 12 of every ferrule must be individually machined after being removed from the mold. Subsequent machining steps may lead to a decrease in uniformity and a decrease in the predictability of performance, as well as a significant increase in production time.
In addition to the disadvantages described above, subsequent machining may also result in movement of the optical fiber bores 11 as the angle is machined into the end face 12, thus adversely affecting the positions of the fibers in the final angled ferrule and decreasing ferrule performance. In particular, the positions of the optical fiber bores 11 after the ferrule is removed from the mold may differ from the positions of the optical fiber bores after the end face is machined to introduce the angle. The movement of the fiber bores 11 may result from the wavering of the fiber bore forming pins throughout the length of the ferrule body or the inability to maintain the pins in straight parallel positions during the molding process. FIGS. 2a and 2b illustrate the positions of the fiber bores 11 before and after machining. FIG. 2a is an end face view of a molded ferrule 10 having a flat end face portion 16 molded perpendicular to a longitudinal axis of the ferrule body. The position of each individual fiber bore 11 results from the position of the corresponding fiber bore forming pin at the interface with the mold insert. Thus, the positions of the fiber bores 11 are controlled to provide a single row of fiber bores positioned along a common axis X. Referring to FIG. 2b, as the flat end face portion 16 is machined to introduce an angle on the end face (the angled portion is indicated generally at reference number 12), the optical fiber bores 11 may move relative to their initial positions due to the inability to maintain the straightness of the fiber bore forming pins during the molding process. While a very slight movement of the fiber bores 11 after polishing may not adversely affect ferrule performance, a movement of more than about 0.1 microns from the initial position of the bore away from or along the common axis 18 result in fiber-to-fiber misalignment and decreased ferrule performance.
Therefore, it is desirable to rapidly and economically produce a large number of substantially identical ferrules having an end face with a predetermined angle relative to the longitudinal axis of the ferrule body, without having to machine each ferrule subsequent to the molding process. Further, it would be desirable to produce a molded ferrule having an end face that does not require machining or polishing the end face, and particularly the region of interest, subsequent to the ferrule molding process. Still further, it would be desirable to mold a multi-fiber ferrule having an angled end face including a plurality of optical fiber bores positioned in controlled and predictable positions along a common axis on the end face of the ferrule using a precision mold insert and molding process to avoid the possibility of fiber bore drift that commonly occurs during machining the end face of the ferrule subsequent to molding. To achieve such a molded ferrule, what is needed is a precision mold insert and associated method for manufacturing a multi-fiber ferrule using the precision insert.